Thermoplastic resin composition

ABSTRACT

Purpose: the purpose of the present invention is to offer resin compositions which have antimicrobial/fungistatic properties which show outstanding dispersion and outstandingly durable performance. Constitution: thermoplastic resin compositions characterized in that an antimicrobial/fungistatic agent, and particularly an inorganic antimicrobial/fungistatic agent, is compounded with a copolymer containing a polyether chain as a constituent unit, such as a polyether/polyamide copolymer, a polyether/polyester copolymer or a polyether urethane, for example, at 0.05-20 wt. %, and thermoplastic resin compositions which comprise a thermoplastic resin, an antimicrobial/fungistatic agent and a copolymer having a polyether chain as a constituent unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to thermoplastic resin compositions, andmore specifically to resin compositions compounded with anantimicrobial/fungistatic agent. The purpose thereof is to offerantimicrobial/fungistatic resin compositions with good dispersion whenused as moulded products or as resin improving agents.

2. Description of the Prior Art

Prior compositions are known for conferring antimicrobial/fungistaticproperties on resins. There are a variety of antimicrobial/fungistaticagents, including natural products, organic compounds and inorganiccompounds; however, in the main, natural products have a low boilingpoint and are difficult to handle. Organic compounds show good phasesolubility with resins, but are not very heat stable, and there is theproblem of a lowering of performance due to decomposition in the processof melting, etc. Inorganic compounds on the other hand are exceedinglystable but have the problem of lowered performance due to poordispersion in resins and elution by water.

The present invention is intended to offer compositions in which theseantimicrobial/antifungal agents disperse well in the resin, are stableand are not eluted to any extent, and have an outstandingly persistenteffect; and we have discovered that this purpose can be achieved bycompounding with specified resins.

SUMMARY OF THE INVENTION

The present invention is a thermoplastic resin composition characterizedin that an antimicrobial/fungistatic agent is compounded at 0.05-20 wt %with a polymer containing a polyether chain as a constituent unit.

The "antimicrobial/fungistatic agent" in the present invention includesnatural products (cypress thiol, chitin, chitosan, etc.), organiccompounds (imidazoles, thiazoles, nitrites, haloalkylthio compounds,pyridines, thiazines, bromine compounds, quaternary ammonium compounds,etc.) and inorganic compounds (zeolites, zirconium phosphate, calciumphosphate, titania and silica, etc.); however, inorganic compoundsincluding silver ions are particularly preferred.

The "polymer containing a polyether chain as a constituent unit" in thepresent invention is a block copolymer in which a polyoxyalkylene chainis connected to another macromolecular chain, or a polymer in whichpolyoxyalkylene chains are linked via linking portions. Examples ofpolyoxyalkylenes here include polyoxyethylene, poly(1,2- and1,3-oxypropylene), polyoxytetramethylene, polyoxyhexamethylene, blockand random copolymers of ethylene oxide and propylene oxide, and blockand random copolymers of ethylene oxide and tetrahydrofuran, etc. Thealkylene portion particularly preferably has 2-4 carbons, andpolyoxyethylene and polyoxytetramethylene are most preferred.

The number average molecular weight of the polyoxyalkylene is preferablyin the range 300-6000, and more preferably 500-4000.

Within the present invention polyether/polyamide block copolymers,polyether/polyester block copolymers and polyether urethanes arepreferably used as the "polymer containing a polyether chain as aconstituent unit".

Within the present invention a "polyether/polyamide block copolymer" isa copolymer in which a poly(alkylene oxide) chain (a) is linked with apolyamide chain (b) which is a polymer of an aminocarboxylic acid or alactam of 6 carbons or a salt of a dicarboxylic acid and a diamine of 6carbons. Copolymers in which (a) and (b) are linked via a dicarboxylicacid of 4-20 carbons are termed generally polyether ester amides. Thesepolymers can be made, for example, by the method of Japanese ExaminedPatent 56-45419. Concrete examples include Pebax (Elf-Atochem), Ely(Ems) and Vestamide (Huls). The types and proportions of the polyamidecomponent and polyether component in block copolymers used in thepresent invention can be selected according to the purpose and end use.

As aminocarboxylic acids or lactams of 6 carbons or salts of adicarboxylic acid and a diamine of 6 carbons here, 11-aminoundecanoicacid, 12-aminododecanoic acid, caprolactam, laurolactam,hexamethylenediamine adipic acid salt and hexamethylenediamine sebacicacid salt are preferably used. Two or more of the aforementionedcomponents (a) can also be used concomitantly.

Within the present invention a "polyether/polyester block copolymer" isa polymer in which a poly(alkylene oxide) chain (a) is linked with apolyester chain (c) which is a polymer of an oxycarboxylic acid of 6carbons or a dihydroxy compound of 2 carbons and an aromaticdicarboxylic acid. Two or more of the aforementioned components (c) canalso be used together. These polymers are discussed in detail, forexample, in the specification of U.S. Pat. No. 4,739,012 (Dupont Co.).Concrete examples include Hytrel (Dupont), Pelprene P series (Toyobo),and Rekuse (Taijin), etc. The percentages by weight of aforementionedcomponent (a) and component (c) in the block copolymer used in thepresent invention can be decided according to the purpose and end use.Even though they are similar thermoplastic elastomers,polyester/polyester block copolymers (e.g. Pelprene S series) givelittle benefit.

Within the present invention a "polyether urethane" is a thermoplasticpolyurethane in which a polyether is used as soft segments; polyestertype or caprolactam type polyurethanes give little benefit. In concreteterms these polyurethanes are ordinarily obtained by reacting an organicdiisocyanate with a polyether of a molecular weight of 500-6000, andoptionally lengthened in the presence of a catalyst. Toluylenediisocyanate and diphenylmethane diisocyanate, etc., are preferablyemployed as the isocyanate, and polytetramethylene glycol andpoly(propylene oxide), etc., as the polyether.

Within the present invention these polyether/polyamide block copolymers,polyether/polyester block copolymers and polyether urethanes can be usedsingly, or in mixtures, or in mixtures of 2 or more block copolymersdiffering in the ratio of soft segments/hard segments in the resin;moreover, blends with other resins within a range within which thepurpose of the present invention is achieved can also be employed.

Within the present invention the antimicrobial/fungistatic agent iscompounded in the proportion 0.05-20 wt % with a polymer containing apolyether. At less than the lower limit the antimicrobial/fungistaticagent has little effect, and at more than the upper limit it isdifficult to disperse adequately even when the present resin isemployed. There is good dispersion in the present resin compositions,and surprisingly the effect is persistent and there is little elution ontreatment with liquids such as water, etc. The detailed reasons for thisare not clear, but the fact that there is little benefit with polyesterelastomers or polyurethane using an aliphatic polyester in soft segmentssuggests that it may be due to coordination and trapping of metal ionsin the ether portion.

Resin compositions of the present invention can be extruded as theystand as sheets, films or fibres, and can be made into injection mouldedproducts having antimicrobial/fungistatic properties, such as wrappingmaterial, wall paper and clothing, etc.; or they can be used incompounds with other thermoplastic resins. Other thermoplastic resinswith which the present resin compositions can be compounded includepolyethylene, polypropylene, poly(vinyl chloride), polycarbonate and ABSresin; they can also be used with other resins with which it isdifficult to compound an antimicrobial/fungistatic agent.

When it is used compounded with another thermoplastic resin, it isdesirable that 0.01-4 parts by weight of antimicrobial/fungistatic agentand 1-20 parts of polymer containing a polyether chain as a constituentunit are compounded with 100 parts of the thermoplastic resin. It isparticularly desirable, when antistatic properties are not needed in thethermoplastic resin composition finally obtained, that the quantity ofpolymer containing a polyether chain as a constituent unit that is addedis 1-15 parts by weight; and 2-10 parts by weight is more desirable.

Prior known antioxidants, thermolysis-preventing agents, ultravioletabsorbing agents, hydrolysis-resistant improvers, colourings (dyes,pigments), antistatic agents, electrical conductors, crystal nucleatingagents, crystallization promoters, plasticizers, lubricants, releaseagents, flame retardants and flame retarding aids, etc., can beincorporated at will into resin compositions of the present inventionwithin ranges which will not detract from the properties of the presentinvention.

EXAMPLES

The present invention is explained in concrete terms below by means ofembodiments, but needless to say the present invention is not restrictedto these alone.

Example 1

The polyether/polyamide block copolymer Pebax A (Elf Atochem) was dried,and then Novalon AG300 (an inorganic compound (zeolite) carrying silverions, mean particle size 0.7 μm, made by Toagosei) was compounded withit at 8 wt %, dry blended, and extruded at 200 C using an extruderfitted with a mixing screw and a 3-mm diameter nozzle at the end, tomake pellets PEBAX A is made of PA-12 blocks of Mn 2600 and Polyethyleneglycol (PEG) blocks of Mn 650. This composition was mixed with 7 timesthe quantity of the same Pebax A, and after blending the pellets to givea final content of Novalon AG300 of 1 wt % it was extruded into a 20 μmthick film in an extruder fitted with a T dye. The film obtained was alight white colour all over and there were no visible particleagglomerations, showing good dispersion.

Example 2

As in example 1, 8 wt % master pellets were made and then these werediluted 8 fold and a 20-m Pebax 1041 film was made, except that SeebioZO-100 (inorganic compound without silver ions, mean particle size 0.4m, made by Hoyu Systems) was used instead of Novalon AG300. Despite thefact that the mean particle size of the antimicrobial/fungistatic agentwas ca. 1/2 of Novalon, many particle agglomerations were visible.

Example 3

When Novalon AG300 was blended with Pebax A at 1 wt % without formingmaster pellets and a 20 μm thick film was made directly by the extruder,the resulting film showed the same good dispersion as in example 1 .

Examples 4-6, Comparison Examples 1-2

Pebax A (polyether/polyamide block copolymer, example 4), Pelprene P-55B(polyether/polyester block copolymer made by Toyobo, example 5),Pelprene S-1001 (polyester/polyester block copolymer made by the samecompany, Comparison Example 1), Toyobo Urethane E3080A (polyetherurethane made by Toyobo, example 6) and E1080A (polyester urethane madeby the same company, Comparison Example 2) were used instead of Pebax Ain example 3, blended with Novalon AGZ330 at 1 wt % and made into 25 μmfilm comprising the respective polymers by the same procedure as inexample 3; slight particle agglomeration was noted in the S-1001 andUrethane E1080A films, but no particle agglomerations were visible inthe other films. NOVALON AGZ 330 has a particle size a little bigger(1,3μ) as AG 300 and contains also zinc in addition to silver.

These films were cut into 50-mm squares which were heat-sealed on 3sides to make 10 small bags from each sheet. Of these, 5 were cleaned byimmersion for 3 hours in warm water at 60 C, followed by drying. Onestrawberry was put into each bag, including the uncleaned bags, and theywere left at room temperature. No great change was visible after 10 daysin strawberries in bags made of film from polyether type polymers,whether washed in warm water or not, whereas strawberries in bags offilm from polyester type polymers washed in warm water were slightlyblack after 1 week, and produced a slightly greenish white mould after10 days.

Example 7

A poly(vinyl chloride) resin composition was obtained by compoundingpoly(vinyl chloride) 100 parts by weight, dioctyl phthallate 35 parts byweight, an epoxy plasticizer 5 parts by weight and an organotinstabilizer 2 parts by weight with 10 parts by weight of the masterpellets of example 1 based on Pebax A with 8% Novalon AG300. Noagglomerates were seen in 1-mm thick sheets made by pressing, and thesheets showed good mechanical strength and antimicrobial properties.

Example 8

100 parts by weight of ABS resin (Toyolac Perel TP10) was blended andpelleted with 10 parts by weight of the master pellets of example 1based on Pebax A with 8% Novalon AG300, and injection moulded to give a1-mm thick sheet. No agglomerates were visible in the resulting sheet,which showed good mechanical strength and antimicrobial properties.

DESCRIPTION OF SPECIFIC EMBODIMENTS

As explained above, by means of the present invention it is possible toobtain thermoplastic resin compositions with outstanding mechanicalproperties, in which an antimicrobial/fungistatic agent is welldispersed and has an effect which persists for a long time.

What is claimed is:
 1. Thermoplastic resin composition in the form of a molded or film product consisting essentially of an antimicrobial/fungistatic agent compounded at 0.05-20 wt % with a polymer containing a polyether chain as a constituent unit.
 2. Thermoplastic film composition according to claim 1, wherein the antimicrobial/fungistatic agent is an inorganic compound which includes silver ions.
 3. Thermoplastic film composition according to claim 1, wherein the polymer containing a polyether chain as a constituent unit is at least one selected from the group consisting of polyether/polyamide block copolymers, polyether/polyester block copolymers and polyether urethanes.
 4. Thermoplastic resin composition in the form of a molded or film product consisting essentially of 0.01-4 parts by weight of an antimicrobial/fungistatic agent and 1-20 parts by weight of a polymer containing a polyether chain as a constituent unit compounded with 100 parts by weight of a thermoplastic resin composition. 